Improvement in interest-calculators



v B. C. COLDWELL.

Improvement in interest-Calculators.

Patented July 16, 1872.

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UNITED STATES PATENT OFFICE.

BENJAMIN O. GOLDWELL, OF LOOKHAVEN, PENNSYLVANIA.

IMPROVEMENT IN INTEREST-CALCULATORS.

$pecificati0n forming part of Letters Patent No. 129,531, dated July 16, 1872.

SPECIFICATION.

To all whom it may concern:

Be it known that I, BENJ. O. (JOLDWELL, of Lockhaven, in the county of Clinton and State of Pennsylvania, have invented a Device for Computing Interest; andI do hereby declare the following to be a full and correct description of the same, reference being had to the accompanying drawing, in which the face of my invention is represented.

My invention relates to a circular card on which the interest on one dollar is reckoned for every three days in a year at from six to twelve per cent., and on which the numbers representing such interest are arranged in concentric circular columns, the first or inside column being for six per cent., the second for seven per cent., and so on up to twelve per cent., and my invention consists in the combination with such a card of a frame with peculiar attachments for pointing out the time, the rate per cent., and the interest.

A is the circular card, the circumference of which is divided into one hundred and twenty equal parts, (that being one-third the number of days in a year at whichinterest is reckoned.) The space allotted to each number is formed by the lines dividing the circumference and those forming the concentric columns. The space near the center is divided into twelve parts or sectors, each of which contains ten of the smaller divisions. These are numbered from 0 to 11, and are intended to represent months. This card is fastened in a frame, B, by a rivet or otherwise, so that it can be turned on its center. On the upper edge of the frame is an are, C, graduated from 0 to 30; and near the lower end is a pointer, D. Swinging from the same center with the card is an arm, E, with a portion of its length graduated from 7 to 12, and in an opening of which is placed a sliding window, F. Through this sliding window the numbers on the card are read, and on the edge of the window is a pointer, a. The frame B has a piece on its back similar to that on its face, and a thin piece of wood or other material is placed between the two, at their upper and lower ends, so as to allow the card to turn freely. This whole frame and its attachments may be made of wood or of any other convenient material.

To find the interest on one dollar fora given time at a given rate per cent., place the pointer D to the given mnnber of months, which are found in the space near the center of the circular card, and if there are any days given set them off on the are C by making the arrow G point to the given number on the arc; the rate per cent. is set off on the arm E by causing the pointer to on the sliding window to coincide with the mark representing the given rate on the arm E, and the amount of in terest is then read through the opening in the sliding window F. Vhen it is desired to find the interest on an amount greater than one dollar the number found in the opening is multiplied by that amount and as the calculations are all carried to three places of decimals, the three right-hand figures must be struck off from the product; the remainder will be dollars and cents.

I claim as my invention The combination, with the circular card A, containing the concentric interest-tables, of the frame B, the arm E, and sliding window F, constructed and arranged substantially as and for the purpose hereinbefore set forth.

The above specification of said invention signed and witnessed at Washington this 5th day of April, A. D. 187 2.

B. G. OOLDWELL.

Witnesses:

W. B. GRosnY, JAMES S. GRINNFLL. 

